(FORT LITTLETON, Pa.) — A retired state trooper allegedly shot and killed a toll collector and a security guard as he was attempting to rob a Pennsylvania Turnpike toll plaza Sunday morning, turnpike officials say.

The shooting was in Fort Littleton, Pennsylvania, about 66 miles west of Harrisburg.

The incident began when the armed suspect, former Trooper Clarence Briggs, 55, confronted two employees — including 55-year-old toll collector Danny Crouse — and tried to tie them up, officials said.

A struggle ensued and Briggs fled, officials said.

Security guard Ronald Heist, 71, a contractor for the turnpike, then drove up to the plaza. Briggs confronted Heist and Crouse there and shot and killed them, officials said.

Heist was a retired police officer. Crouse had been a toll collector there for less than three months, officials said.

A responding trooper exchanged gunfire with Briggs and Briggs died at the scene.

Briggs served as a state trooper for 26 years and retired in January 2012 with an honorable discharge, officials said this afternoon. He was in Troop T, which is responsible for policing the turnpike.

The other turnpike employee who was initially confronted by Briggs survived the robbery attempt and is OK, officials said.

“We are all deeply saddened by this horrific tragedy,” Turnpike Chairman Sean Logan said in a statement earlier Sunday. “Our thoughts and prayers are with the family and friends of the deceased victims, the turnpike employee and the contractor. We cannot imagine what the families must be feeling right now.

“Certainly, today will be a day that none of us will soon forget,” Logan said.